Batch contactor

Both batch contactors as well as chromatographic columns have been suggested for decolorization [130]. Nevertheless, to remove color with a single adsorbent was... 

The batch contactor is limited to use with reactions that go to completion in a single stage or in relatively few stages. Difficulties may also arise with batch contactors if resin regeneration requires a greater number of equilibrium stages than the service portion of the cycle. 

A batch of m-chloroaniline is to be produced by reducing m-nitro-chlorobenzene (MNCB) with an aqneous solution of sodium disulfide (Na2S2) in a fully baffled 2000 L mechanically agitated batch contactor at 105°C. The reaction is known to be restricted to the continuous aqueous phase (i.e., phase 2). The regime of this reaction (for 100% conversion with stoichiometric quantities of reactants) was shown to shift from 3 (fast) at the start to 1-2 at the end. Using this information and the following data, calculate the reaction time. 

FIG. 23"37 Equipment for liquid/liquid reactions, a) Batch stirred sulfonator. (h) Raining bucket (RTL S A, London), (c) Spray tower with Loth phases dispersed. (d) Two-section packed tower with light phase dispersed, (e) Sieve tray tower with light phase dispersed, (f ) Rotating disk contactor (RDC) (Escher B V, Holland). (g) Oldshue-Rushton extractor (Mixing Equipment Co. ). 

There are many reasons why chemical synthesis is advantageously performed in flow mode using a micro-contactor (or microreactor) rather than in a round-bottomed flask, well or vessel. In fact, if it was not for a long history of batch mode chemistry and the convenience of a handsized flask, the case would need to be made for employing batch methods. 

Mixed Flow G/Batch Uniform L—Absorption + Reaction in a Batch Agitated Tank Contactor... 

Holdup and Flooding. The volume fraction of the dispersed phase, commonly known as the holdup h. can be adjusted in a batch extractor by means of the relative volumes of each liquid phase added. However, in a countercurrent column contactor, the holdup of the dispersed phase is considerably less than this, because the dispersed drops travel quite fast through the continuous phase and therefore have a relatively short residence time in the equipment. The holdup is related to the superficial velocities V of each phase, defined as the flow rate per unit cross section of the contactor, and to a slip velocity Us ... 

Dimitrov, K., Rollet, V., Saboni, A. and Alexandrova, S. (2008) Recovery of nickel from sulphate media by batch pertraction in a rotating film contactor using Cyanex 302 as a carrier. Chemical Engineering and Processing, 47, 1562. 

The holdup is just as important as r/32 in Eq. (12) for specific interfacial area. In a batch extraction it is simply determined by the amounts of each phase added, but in many types of continuous countercurrent contactor it is a complex function of flow rates, drop size, etc. The slip velocity us for countercurrent flow is defined in terms of the superficial velocities U (flow rates per unit cross-sectional area) of each phase,... 

Hamill NA, Weatherley LR, Hardacre C (2001) Use of a Batch Rotating Photocata-lytic Contactor for the Degradation of Organic Pollutants in Wastewater, Appl. Cat. B Environ. 30 49-60. 

Here mp is the total mass of the particles ivith radius R placed in the contactor ivith a useful volume V. In some cases, the surface diffusion is considered the sloivest process because organic components such as hydrocarbons are generally strongly adsorbed on activated carbon [3.65, 3.66]. Indeed, we can consider here that, at the surface of the particle, the adsorption equilibrium is achieved faster than the surface diffusion process. In these conditions the batch model equations are ... 

Dimitrov K, Alexandrova S, Saboni A, Debray E, and Boyadzhiev L. Recovery of zinc from chloride media by batch pertraction in a rotating film contactor. J Mem Sci, 2002 207(1) 119-127. 

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